1. Field of the Invention
This invention relates to receiving units for timepieces, and specifically to improved receiving units for a self-winding mechanism of self-winding timepieces.
2. Description of the Prior Art
Heretofore, a variety of improvements were contrived for the wrist watches, and particularly for the self-winding timepieces. Among them, the self-winding timepieces of the reverser type required simplified mechanical parts and were suited for reducing the manufacturing cost. It has also been known that the winding performance is not lost even with the self-winding timepieces which wind in one direction only.
The conventional timepieces of this sort, however, presented a problem when it was attempted to further reduce the manufacturing cost. FIG. 1 shows a wheel train of a conventional self-winding mechanism of the reverser type which winds in one direction only. In the drawing, reference numeral 2 denotes a weight wheel pinion in a self-winding mechanism, which is in mesh with a reverser 4. The reverser 4 is guided through an elongated hole 3a of a receiving unit 3 and a guide portion 22a of a metallic receiving unit 22, and is biased by a reverser spring 19. One end of the reverser spring 19 is attached by caulking to a slit formed in the metallic receiving unit 22. The motion of the reverser 4 is transmitted to a square-holed wheel (not shown) through reduction wheels 6 and 7. The reduction wheel 6 is engaged with a click 21 of a self-winding mechanism, and is pivotted to the receiving unit 3 being urged by a click spring 20. The click spring 20 is mounted on the receiving unit 3 by means of a pin 20a and a screw 20b.
It was required that the reverser spring 19 and the click spring 20 of the aforementioned prior art must have a resilient force which was as small as about 1 gram, so that the winding performance of the self-winding mechanism was not decreased. Therefore, these springs 19 and 20 usually consisted of a leaf spring having a thickness of about 50 microns. It was, however, very difficult to prepare such springs because of warping of the spring material and dispersion in quality developed during the step of bending. The reverser spring 19 and the click spring 20 could be secured as shown in FIG. 1, requiring clumsy operation in attaining the proper position and in performing the assembling, eventually making it difficult to automatically manufacture the timepieces in large quantity. Furthermore, the receiving unit required slits for fastening these springs, pins for determining the positions or screw-taps. For this purpose, increased processing steps were needed, and a special processing must be effected to attain high dimensional precision in the hole for rotatably holding the reverser shaft and in the guide portions of the self-winding mechanism, such as holes for holding the reduction wheels, thereby to obtain smooth sliding surfaces.